Summary of July 16-19, 2013 Wisconsin Heat Wave (Updated 07/25)

Wisconsin experienced a long-duration heat wave during the period of July 16-19, 2013. Temperatures were well above normal and humidity levels were elevated. However, this July, 2013 heat wave was not as long or as bad as the July, 2012 heat wave.

The Wisconsin Department of Health Services in Madison reported 3 confirmed heat-related fatalities: 1 in Polk County, 1 in Manitowoc County, and 1 in Tempealeau County. Additionally, there were an additional 5 probable heat-related fatalities in Milwaukee County that have not been confirmed.

Below is a brief summary of the maximum heat indices observed at sites which have automated observation equipment. Additionally, afternoon dew-point temperatures, prevailing wind direction and wind speeds are provided. Finally, the maximum and minimum air temperatures are depicted. Notice how warm the overnight temperatures were - especially during the overnight hours ending Friday morning the 19th.

For Southcentral and Southeast Wisconsin...the Milwaukee/Sullivan NWS Forecast Office initially mentioned the possible need for a Heat Advisory at 4 am CDT on Sunday July 15th in a Hazardous Weather Statement (HWO). This office subsequently issued Heat Advisories Tuesday morning for the period of Tuesday the 16th through Friday the 19th for heat indices to reach at least 95 to 99, with local spots reaching 100 to 105 due to maturing corn crops evaporating moisture into the air. Heat Advisories are issued when heat indices are expected to reach over 100 or when 4 consecutive days of heat indices of 95 to 99 are expected.

July 16-19, 2013 Heat Wave

Maximum Heat Indices at Airports (AP)

16-Jul

17-Jul

18-Jul

19-Jul

Milwaukee AP

101

102

102

101

Timmerman AP

95

97

94

94

Madison AP

100

99

97

96

WFO Sullivan

108

108

108

102

Kenosha AP

101

101

100

100

Racine AP

94

102

100

97

Burlington

96

96

97

94

Janesville AP

99

100

100

97

Monroe AP

96

97

98

95

Lone Rock AP

102

105

102

97

Dells AP

95

96

96

92

Watertown AP

100

101

100

96

West Bend AP

93

94

95

91

Fond du Lac AP

96

98

97

94

Sheboygan AP

100

100

101

97

Dewpoints

70s

u60s-l70s

m60s-l70s

m60s-l70s

Wind Direction

SW-W

SW-W

SW

SW

Wind Speed

5-15 mph

10-20 mph

15-25 mph

15-30 mph

July 16-19, 2013 Heat Wave

Max & Min Air Temperatures (excluding cooling evening 19th)

16-Jul

17-Jul

18-Jul

19-Jul

Milwaukee AP

93/75

95/79

95/79

94/80

Timmermman AP

90/73

93/75

91/73

91/77

Madison AP

92/74

93/74

92/75

91/80

WFO Sullivan

93/73

94/73

95/73

92/70

Kenosha AP

93/72

93/74

95/73

94/79

Racine AP

90/75

93/77

94/77

94/79

Burlington

89/66

90/70

90/70

89/74

Janesville AP

93/72

95/73

95/73

93/77

Monroe AP

91/74

93/77

93/76

90/75

Lone Rock AP

93/69

96/70

95/70

93/75

Dells AP

91/72

91/73

92/73

91/77

Watertown AP

90/71

92/73

92/73

89/76

West Bend AP

90/70

91/73

91/72

91/79

Fond du Lac AP

90/70

92/75

93/75

91/77

Sheboygan AP

90/69

94/72

94/71

93/79

Record high minimum temperatures were tied or set at Milwaukee Mitchell Field for 3 consecutive calendar days:

2013 Date

Min Temp

Status

Year

Old Record Value

July 17

79

tie

1878

-

July 18

79

new

1942

77

July 19

79

tie

1935

-

Interestingly, the minimum overnight heat index (HI) values at Milwaukee Mitchell Field were elevated (see table below). Consequently, in the Milwaukee city area one had a hard time cooling off at night if they didn't have air-conditioning. This is why a long-duration heat wave can be deadly.

Date

Min HI

Time

16

76

6 am CDT

17

82

6am CDT

18

82

6 am CDT

19

84

6 am CDT

Below are graphics depicting maximum heat indices across Wisconsin, left to right, for the period of Tuesday July 16th through Friday July 19th. Click on images for larger versions.